The writing process for the majority of Metallicaâs albums have followed the same process. A large slew of guitar riffs written primarily by James Hetfield, sometimes Kirk Hammett, and rarely the bandâs bass player, (that now being bass virtuoso Robert Trujillo) are reviewed and selected.
1 Delhi is most polluted city in the world in PM2.5 concentrations. 2  Half of the top 20 most polluted cities were in India, according to data.  PM2.5 is considered most harmful to health.
Pollution. In terms of pollution, Tucson is one of the best cities to live. The American Lung Association has named Tucson as one of the least polluted cities in the U.S. The air in the city is considered cleaner than in other major cities like Las Vegas.